The role of Paraxial Protocadherin in selective adhesion and cell movements of the mesoderm during Xenopus gastrulation

(P) under bar ar (a) under bar xial (P) under bar roto (c) under bar adheri n (PAPC) encodes a transmembrane protein expressed initially in Spemann's o rganizer and then in paraxial mesoderm, Together with another member of the protocadherin family, <(Ax)under bar>ial (P) under bar roto (c) under bar amdherin (AXPC), it subdivides gastrulating mesoderm into paraxial and axia l domains. PAPC has potent homotypic cell adhesion activity in cell dissoci ation and reaggregation assays. Gain- and loss-of-function microinjection s tudies indicate that PAPC plays an important role in the convergence and ex tension movements that drive Xenopus gastrulation. Thus, PAPC is not only a n adhesion molecule but also a component of the machinery that drives gastr ulation movements in Xenopus. PAPC may provide a link between regulatory ge nes in Spemann's organizer and the execution of cell behaviors during morph ogenesis.